1. Field of the Invention
The present invention relates to a wind turbine generator in which heat generated in equipment during operation is cooled by introducing external air.
2. Description of Related Art
A standard wind turbine generator is an apparatus in which a rotor head provided with turbine blades rotates by receiving wind force, and a generator is driven by increasing the speed of this rotation by using a gear box, etc., thus generating power. The rotor head is mounted at an end portion of a nacelle, which is installed at the top of a tower erected on the ground, etc. and which is capable of yawing, and is supported so as to be rotatable about a substantially horizontal, laterally oriented rotation axis.
In general, a monopole-type steel tower employing a cylindrical tower shell is often employed as the above-described tower, and the structure thereof is such that a base plate provided at the bottom end of the tower shell is secured to a steel-reinforced concrete foundation with anchoring bolts. Because heat-generating electrical equipment, such as a converter and a transformer, is installed inside such a wind turbine generator in addition to the generator, such electrical equipment needs to be appropriately cooled to continue stable operation.
In a conventional simple cooling structure, a ventilating fan is installed inside the tower or the nacelle, and the heat-generating electrical equipment is cooled by force-feeding cool external air into the interior. For example, as disclosed in U.S. Pat. No. 7,168,251, there is a known cooling structure in which cooling liquid, such as water, oil, etc., is circulated inside the heat-generating electrical equipment with a circulation pump; heat exchange is performed with the cooling liquid supplied for cooling at a heat exchanger; and the exhaust heat therefrom is externally released.
However, when a ventilating fan is installed or cooling liquid is circulated to serve as a cooling structure for cooling heat-generating electrical equipment, as described above, the configuration thereof inevitably becomes complicated, and, in addition, power generated by the wind turbine generator must be consumed to drive the ventilating fan or the circulation pump, which is not desirable.
In the case of a liquid cooling system, there is a problem in that, in addition to having a complex structure to begin with, by installing a heat exchanger, the nacelle and its surroundings are increased in size and also become heavier; therefore, the strength of the tower inevitably needs to be increased. Additionally, because the heat exchanger is structured so as to be exposed to external air, in the case in which the wind turbine generator is installed at the coast or at sea, the heat exchanger must be sufficiently protected against corrosion; and the building cost of the wind turbine generator is increased due to these factors.
In the case in which introducing vents for taking in the external wind and exhaust vents for exhausting the internal air are provided, the number of these openings and the area of the openings must be minimized, and the strength of the tower must be ensured.